Abii
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Phased Array is very specialized. Even UT technicians with 20 years in the field have to go back to school to get retrained. The basic idea is that the transducer sends multiple beams into the object instead of the usual solitary beam sent with a traditional FLAW method. It decreases time and you also don't need to move the transducer around. You just place it and the beams do their thing. It's also more accurate. Phased Array is slowly taking over both UT and Radiography.It's first time I'm hearing about phased array being used in NDT methods, that's interesting. How does it work? About radiography, if I'm not mistaken, gamma always works better than x-rays isn't it? I knew about that Acoustic Emission test, it's very awesome, first time I read it, I couldn't believe it's possible to detect sound waves emitted from a corrosion process or a micro crack moving inside the structure.
Visual inspection is much easier, but shouldn't they give less money for it?
So you don't use MT method much right? since it can only detect faults and cracks a few millimeters under the surface and not those deep in the structure.
Frost & Sullivan: Replacement of Radiography by Phased Array Ultrasonic Testing Drives Global Ultrasonic NDT Equipment Market
With X-Ray the problem is portability. When you're on the field or 70 feet up on a tank, you can't use an X-Ray machine. X-Ray uses electricity of course and it's less dangerous, but not at all portable. With gamma you have a 50 pound camera and you can take it anywhere. The problem is radiation and the possibility of a major accident is always present.
Acoustic Emission is extremely cost effective. The way it was explained to me was that it can be done on live tanks with all sorts of products inside. Traditionally you'd have to empty the tank, clean it, send in visual inspectors and finally send in the gamma/MPI crews. That's millions upon millions of dollars. With AE you just place the microphones, connect them to amplifiers and voila! You can give the client a report on the condition of the tank without emptying the damn monster. They can decide if it needs to be refurbished or not, but the inspection didn't cost them an arm and a leg. This means more inspections can be done as companies won't be afraid of costs anymore. The guy that was explaining it to me said the sound of a water drop was the same as a canon going off 1 meter in front of you!!! They could pin point where that water drop originated from too. Amazing.
MT is done a lot in fabrication shops actually. But it's mostly done on misc stuff. When it comes to pipe it's mostly gamma (to meet code requirements). We do MT on pipe that can't be X-rayed though (i.e. pipe smaller than 2 inch or pipe with a fucked up weld that can't be shot). MT is used a lot during shut downs (when plants and refineries shut down for annual maintenance).
Visual inspection is the highest paying method actually. It's not even close. Quality control people, lead inspectors etc... all need to be certified to different visual inspection codes. Even engineers can't go straight into visual inspection. For example, in order to get your API 510 certification, this is what you need to do:
API 510 Pressure Vessel Inspector Program - Qualification Requirements
API certified inspectors make more than engineers here.